Rock drill bit

ABSTRACT

Rock drill bit adapted for use in percussion drilling apparatus, the drill bit having a body generally in the form of a body of revolution which is convex in an axial direction and which has an annular edge of largest diameter lying on a transverse plane disposed normal to the axis of rotation of the bit. A plurality of hard, wear-resistant inserts are mounted on the outer surface of the body of the bit adjacent the said transverse plane.

United States Patent 11 1 1111 3,800,892

Fischer 1 Apr. 2, 1974 ROCK DRILL BIT 2,689,108 9 1954 Haglund 175 411 x 3,311,181 3/1967 Fowler 1 175/410 [75] Inventor: Ernst wcnt Ausma 3,346,060 1967 Beyer 1 175 410 73 Assigneez Gebr, Bohler & Cm 3,583,504 6/1971 Aalund 175/410 gkfifigesellschafl, Kapfenberg, FOREIGN PATENTS OR APPLICATIONS Sula 645,377 9 1964 Belgium 175 410 [22] Filed: June 4, 1971 [211 App] No 150 134 Primary Examiner-Ernest R. Purser Assistant Examiner-Richard E. Favreau Foreign Application Priority Data 57] ABSTRACT .l 5 I970 A 5041 um usma Rock drill bit adapted for use in percussion drilling ap- 52 us. c1. 175/410 175/418 Paratus, the having a body generally in the 51 Int. 122 111 13/01 form of a body Of revolution which is convex in [58] Field of Search H's/410 l 412 409 axial direction and which has an annular edge of larg- I I I est diameter lying on a transverse plane disposed nor- [56] Reierences Cited mal to the axis of rotation of the bit. A plurality of hard, wear-resistant inserts are mounted on the outer UNITED STATES PATENTS surface of the body of the bit adjacent the said trans- 3,185,228 5 1965 Kelly 175/410 erse 1am 3,536,150 l0/l970 Stebley l/4l0 X v p 3,548,959 12/1970 Hasiba /410 4 Claims, 1 Drawing Figure ROCK DRILL BIT This invention relates to a rock drill bit, in particular a bit for percussion drilling apparatus, in which the end surface of the body of the drill bit is provided with wear resistant inserts shaped in the form of pins, the circumference of the bit being limited by an outer edge, there being wear resistant pins mounted at such outer edge.

A percussion drill bit is known in which there are provided insert pins at the outer edge, the insert pins being disposed in radial axial planes, but they are positioned in such planes diagonally with respect to the longitudinal axis of the bit. The wall strengths of the drill bit body alongside the insert pins are inferior, and so the percussion drill bit has the disadvantage that with strong percussive stresses the drill bit body next to the insert pins is deformed; because of this the insert pins become loosened from the body of the bit.

With another known drill bit for rotating drills, the wear resistant inserts such as diamonds are positioned at the end surface of the drill bit body, which is built like a ball. The diamonds are positioned at the outer edge of the drill bit body, overlapping diamond inserts being positioned diagonally of the longitudinal axis of the body. If one were to make percussion drill bits in this manner, such drill bits would have the same disadvantage as that described above in connection with known percussion drill bits.

In accordance with the invention, this disadvantage of the aforementioned rock drill bit can be overcome by disposing hard, wear-resistant insert pins on the outer surface of the body of the bit in the plane normal to the longitudinal axis of the bit adjacent the largest diametered zone or edge of the body of the bit. Compared with the aforementioned described known drill bits, the drill bit of the instant invention gives the surprising technical effect that even under strong hitting stress the drill bit body alongside the inset pins will not be substantially deformed, and will provide the assurance that the inserts will be held tight on the drill bit body.

Further details of the present rock drill crown are described with the illustrative embodiment, which is shown in the accompanying drawing.

The single FIGURE of the drawing shows a rock drill bit half in an elevational view and half in an axial sectional view.

Turning now to the drawing, the illustrative drill bit, the body 1 of which may be made of steel, is in the form of a body of revolution having a longitudinal axis a-b, the upper portion 9 of the body being in the form of a first upper frustum of a cone, a second, almost cylindrical, intermediate portion 8 of frusto-conical shape having an apex angle smaller than that of the upper portion of the body, and a lower end portion having a surface 2 at least generally in the form of a part of a sphere. The outer junction between portion 8 and surface 2 is a circle 6 lying in a plane normal to axis a-b; circle 6 thus defines a limiting outer edge of the drill bit. The upper portion 9 of the body 1 is provided with an axial threaded bore 10 for attachment of the drill bit to a drill rod (not shown). The lower end of the drill bit is provided with a plurality of hard inserts 3 made, for example, of sintered tungsten carbide, the inserts 3 being generally in the form of cylindrical pins disposed normal to the part-spherical surface 2, the lower ends of pins 3 being rounded.

The drill bit is also provided with further hardened inserts in the form of cylindrical pins which are disposed generally above the inserts 3. A first such set of inserts, designated 4, is disposed in a ring (one insert is shown at the left) coaxial of the axis a-b, the inserts 4 having their longitudinal axes disposed parallel to the axis a-b, the lower ends of inserts 4 having rounded outer and lower surfaces 4. In other words, the overlapping ends of the aforementioned inserts 4 are rounded out only at the side 4 which is turned away from the drill bit body 1. The outer ends of inserts 3 and the surface 4 of each insert 4 lie on an imaginary surface below and radially outwardly of and parallel to surface 2 of the body 1.

Above the inserts 4 and radially outwardly with respect thereto there is a second annular row of hardened inserts 5 in the form of cylindrical pins, the longitudinal axes of the pins 5 extending radially of the axis a-b, and being located in a transverse plane c-d which lies normal to the axis a-b. The upper surfaces of the inserts 5 lie substantially in the plane of circle 6, which as we have seen marks the border between the lower frusto-conical zone 8 and the lowermost part-spherical end of the drill bit having the surface 2. Each of the inserts 5 has a rounded outer end surface 5' which is a part-spherical surface extending radially outwardly and upwardly from the lower surface of the insert 5 to an outer upper edge which lies substantially on the plane 6. In other words, the outer edges of the insert pins 5 are rounded out only at the side 5' which is turned from the drill bit body. Such upper outer edges of pins 5 extend radially outwardly beyond the surface of body 1 by a distance s.

lt is a feature of the present invention that a plane containing the upper edge of each insert 5 and tangent to the lower outer surface 4 of the next adjacent insert 4 makes an angle a with the longitudinal axis a-b on the drill bit which lies between 25 and 45. Preferably the angle a is approximately 35.

In the part 8 of the drill bit there are provided, for purposes of protecting it, additional overlapping inserts 12 which extend radially outwardly of the outer surface of the drill bit by a distance which substantially equals the distances by which the upper outer corners of the inserts 5 extend beyond the surface of the drill bit body. Instead of the round inserts 3, 4, and 12, angular inserts may be provided. Such angular inserts may, for instance, be 6 or 8 sided figures in cross-section. Such angular inserts may also be mounted, in the same manner as the round inserts, on the drill bit body in cylindrical holes in which they are held by solder. The drill bit body is provided with scavenging channels 7 which are positioned normal to the end surface 2 and diagonal to the longitudinal axis a-b of the drill body. lnstead of the scavenging channels, or besides them an axial scavenging channel (not shown) may also be provided. The drill bit body 1 also has conventional longitudinal extending slots 11, which are used divert the detritus formed by the drilling operation.

The insert pins 5, within the scope of the invention, may be disposed diagonally of the longitudinal axis a-b rather than radially thereof as shown in the drawings and described above.

Although the invention is illustrated and described with reference to one preferred embodiment thereof, it

is to be expressly understood that it is in no way limited to the disclosure of such a preferred embodiment, but is capable of numerous modifications within the scope of the appended claims.

What is claimed is:

1. A rock drill bit adapted for use in percussion drilling apparatus, the drill bit having a body at least generally in the form of a body of revolution rotatable about its longitudinal axis, the body being generally longitudinally convex and having an outer edge of largest diameter disposed generally in a transverse plane normal to the longitudinal axis of the body, and hard, wearresistant inserts mounted on the outer surface of the body adjacent the said transverse plane, the radially outer ends of the inserts lying in said transverse plane, said radially outer ends of the inserts being rounded axially of the drill bit only on the radially outer and lower sides thereof.

2. A rock drill according to claim 1, wherein the radially outer ends of the inserts are rounded radially inwardly in a direction axially downwardly of the drill bit from the largest-diametered outer edge of the body.

3. A rock drill bit according to claim 1, wherein a plane passing through the outer edge of the body and tangent to an imaginary surface of revolution representing the effective surface of the lower end of the drill bit meet the longitudinal axis of the drill bit body at an included angle of from 25 to 45.

4. A rock drill bit according to claim 3, wherein said included angle is approximately 35. 

1. A rock drill bit adapted for use in percussion drilling apparatus, the drill bit having a body at least generally in the form of a body of revolution rotatable about its longitudinal axis, the body being generally longitudinally convex and having an outer edge of largest diameter disposed generally in a transverse plane normal to the longitudinal axis of the body, and hard, wear-resistant inserts mounted on the outer surface of the body adjacent the said transverse plane, the radially outer ends of the inserts lying in said transverse plane, said radially outer ends of the inserts being rounded axially of the drill bit only on the radially outer and lower sides thereof.
 2. A rock drill according to claim 1, wherein the radially outer ends of the inserts are rounded radially inwardly in a direction axially downwardly of the drill bit from the largest-diametered outer edge of the body.
 3. A rock drill bit according to claim 1, wherein a plane passing through the outer edge of the body and tangent to an imaginary surface of revolution representing the effective surface of the lower end of the drill bit meet the longitudinal axis of the drill bit body at an included angle of from 25* to 45*.
 4. A rock drill bit according to claim 3, wherein said included angle is approximately 35*. 